This invention relates to the treating of textile material. More specifically, this invention relates to foam dyeing of textile material, such as carpets.
Numerous techniques have been used for treating or dyeing textile material such as carpet. A common technique is the well known and popular "TAK" process wherein dye is dropped or splattered onto the carpet web previously flooded with gum. This is disadvantageous in that it requires a great amount of gum, which in turn produces a large amount of effluent and necessitates a great amount of energy for steam setting the dye and for drying the carpet. Additionally, the use of a roller and doctor blade or similar types of dye applicating arrangements for applying dye and the period for drying are limiting factors in terms of the speed at which the carpet is conveyed through the system and consequently limit the rate of carpet production.
Foam dyeing represents an attempt to overcome several of the above-mentioned disadvantages common to most dyeing processes. Although various foam dyeing techniques have been generally useful in avoiding several of the disadvantages associated with conventional dyeing techniques, they are often limited to the production of patterns having random dyeing affects. Generally, such techniques have been unsuitable for patterns requiring sharp resolution for intricate or detailed patterns. Further, the requirement for adding relatively large quantities of foam generators and foam stabilizers adds to the production costs of such techniques. Additionally, most foam dyeing requires pumping foam from remote foam generators which are disadvantageous not only because the foam must have stabilizers to prevent its dissipation when it is pumped, but because it is more difficult to change colors or achieve add on when the foam is then sported over long distances via a pipe or tube. The flow of foam in such systems requires dumping of all foam left in the tube resulting in costly wastage.
Some years ago foam dyeing was introduced for batch dyeing piece goods. The purpose of the process was to carry out aqueous dyeing with the very minimum use of water, and initial attempts utilized as little as 1:1 volume ratios and less. However, equal parts of water neither fully nor uniformly wet out fabric. As a result the idea of spreading the effective surface area of the water by creating foam bubbles was developed. The dye solution containing a foam surfactant was applied to the fabric under nonfixation conditions, followed by the mechanical action of running the fabric. The foam which developed served to move the dye throughout all the fibers prior to reaching fixation conditions. After uniform distribution of the dye was achieved, hot air was introduced to raise the temperature for fixation. This process, in effect, was the forerunner of the foam dyeing which is seen today.
Foam dyeing presents several advantages over conventional techniques. Four to five hundred percent dye pickup is possible in the continuous foam dyeing of carpet, and while there is some controversy about the amount of foam pickup required to produce a satisfactory dyeing, there is no doubt about the fact that considerably less water must be heated in the steamer when applying dye with foam. Even if as much as 200% pickup is used, a minimum 50% reduction in energy demand is achieved for heating the dyebath which has been placed on the carpet. On the basis of requirements of 1 Btu per degree per pound of water, a change from five pounds to two pounds of water pickup per pound of carpet represents a decrease from 650 to 260 Btu per pound of carpet to heat the water to 212.degree. F. Thus, steam consumption for heating the dyebath on carpet weighing two pounds per square yard would be reduced from 6,336 pounds to 2,495 pounds per hour if linear speed were 60 feet per minute.
Substantial increases in carpet productivity can be achieved since carpet lines can be constructed to operate at 100 feet per minute and more. Existing lines to which foam applications have been added have been speeded up to 60 feet per minute. When this is measured against 30 to 40 feet per minute on the average line currently in place, the productivity advantages for foam ranges are enormous.
It has been found that full penetration of acid dye into the fiber filament can be achieved in about two and one-half to three minutes in an atmospheric steamer. Thus, existing 80 meter loop steamers or 200 foot horizontal steamers can easily handle the higher running speeds.
The most rapid speeds are made possible partially because lower wet pickup provides more rapid heat-up to dyeing temperatures, as well as easier washing requirements due to the elimination of gums.
The firm body produced by many foam systems has eliminated the need to use gums to increase bath viscosity. This is a significant cost saving. The firmness of the foam can be varied to suit any particular purpose simply by increasing the blow ratio or by adding foam stabilizers. In the latter, a small amount of gum will significantly increase firmness. Higher concentrations of chemicals ore more mechanical action will also develop greater foam stability.
Gums are frequently used to create styling effects such as those achieved with gum layers, and here again similar styling effects are being achieved with foam. The cost savings generated by using air to replace gums are obvious.
Substantial savings in dye costs can result from foam systems. The cost reduction occurs because all of the dye applied is fully utilized. Existing methods of dye application frequently allow considerable losses, due to run-off resulting from the high pickups which are used. Excess dye and residuals in pipes and tanks are also minimized. It has been proven in practice that there is as much as a 10 to 15% reduction in dye cost when dyeing solid colors and even more when dyeing multicolor. When foam systems are used for dyeing, savings in rinse water are also seen. This is because gums have been eliminated and all the dye has been fully fixed. Rather than full immersion washers with various types of mechanical agitation, simple sprays and vacuum extractors appear to be all that is needed. Therefore, the reduced water load represents good water conservation practice as well as an economic advantage.
While waste steam reduction may not be a significant factor at all locations, it will certainly be more of a concern in the future. By using foam for carpet dyeing, the waste stream is reduced considerably in volume, and treatments related to gum disposal and excessive dye runoff are eliminated. Mills now paying tax on every gallon of wastewater entering the sewage stream will certainly appreciate saving this nonproductive cost. And as discussed in the discussion on washing, the use of foam to replace fluid water for washing again cuts the waste stream considerably.
Any fluid system containing dye, whether it be water, foam or solvent, must be applied uniformly to the fabric, both side-to-side and end-to-end. Whatever mechanical device is used, it must deposit the fluid uniformly. In point of fact, the method of applying foam is the key difference between the several foam dyeing machines being promoted today. Foam prepared for deposition onto fabric should be uniform. Every liter must contain exactly the same amount of dye to insure uniform dyeing.
The preparation of uniform foam depends on delivering exactly constant quantities of dye solution and air to be mechanically blended to a uniform product. The blow ratio, or specific gravity, of the foam is a controlling factor, and must remain constant throughout the run.
Two known systems used to externally generate foam include the rotary mixer and the static generator. The former delivers both air and dye liquor to the foam generator in precisely metered amounts, thence through a hose to the point of use. The degree of mechanical action in the foam head determines the consistency of the foam, large or small bubbles, stiff or loose foam. The pressure which is generated in the foam head must be reduced to atmospheric pressure at the point of delivery, and this is largely controlled by the length of delivery hose.
The static foamer does not build any significant pressure, and uniformity of dye being delivered as foam is controlled by precise metering of the prepared dye solution. Air is delivered under a fixed pressure which automatically provides the desired blow ratio and bubble size.
The two described systems of generating foam for dyeing are external foam generating systems. Another type of foam generating system may be described as an in-situ foam generators. In one known in-situ method air jets within a trough of dye create the foam simply by blowing through the dyebath containing a foaming chemical. Delivery of dye is controlled by maintaining a constant level of dyebath in the dye trough. A constant feed of air to the trough then controls the amount of foam which is generated, and thus delivery of dye to the fabric. The present invention relates to in-situ foam generation wherein foam is produced by mixing air and dye solution at the spray nozzle through a jet. A fine foam in the form of a spray is delivered to the fabric as it passes under the jets. By varying air pressure, penetration and coverage can be changed. By varying the quantity of dye delivered, add-on can be controlled.
What is believed to be one of the first successful use of foam for dyeing carpets was by Galaxy Carpets of Dalton, Ga., to produce multicolor designs. The method used was the patented system developed by United Merchants & Manufacturers, Inc., described in U.S. Pat. No. 4,282,729. In this patent, foam is generated externally using a rotary head mixer then delivered through a pipe (21) to the trough (10). At points 22 and 23, concentrated dye is injected into the foam stream. As the foam is delivered at point 24, it falls onto the triangular shaped disc (30). The disc makes a rotating motion as the whole assembly traverses the width of the carpet, creating a foam/dye reservoir. The injected foam can be either clear or colored and the shape of the distribution disc can be changed, with each modification creating a different pattern effect. More dye streams can be injected into the foam stream to give greater color variation if desired. The foam blade can be raised or lowered to control the amount of foam left on the carpet face.
Following application, the foam is immediately collapsed by vacuum. A light nip roll section follows to even out any dye fluid nonuniformities, particularly at the selvages, and to provide a pulling action on the carpet. Steam fixation, washing and drying complete the operation.
Kusters is a manufacturer which has been active in continuous carpet dyeing equipment since 1967. In the Kusters machine, foam is generated externally and piped to a reservoir where it is doctored onto the carpet applicator roll. The film of foam is accurately metered onto the roll through an adjustable gap in the bottom of the foam box. This apparatus is described in U.S. Pat. No. 4,275,683.
It is a general object of the present invention to provide a new and improved method and apparatus for foam dyeing of textile material.
Another object of the present invention is to provide for the dyeing of textile material with a relatively low amount of water and energy consumption.
A further object of the present invention is to provide for the dyeing of textile materials with only a minimal amount of effluent produced.
A still further object of the present invention is to provide for the dyeing of textile materials with sharp patterns having a high degree of resolution.
Yet another object of the present invention is to provide for the dyeing of textile materials wherein the dye is used in a highly efficient manner with very little of the dye wasted.
Another object of the present invention is to minimize the drying time of a dyeing process so as to allow an increased rate of production.
Yet another object of the present invention is to provide for the dyeing of textile materials with patterns which may be changed very quickly.
A still further object of the present invention is to provide solid color dyeing wherein color changeover can be accomplished with minimum waste of dye liquor.
Still another object of the present invention is to provide an improved method and apparatus for foam dyeing of carpet.